1. The Field of the Invention
The invention relates to a process of producing a glass-ceramic, the glass-ceramic made by the process, and the uses of the glass-ceramic.
2. The Description of the Related Art
Glass-ceramics containing microcrystalline BaTiO3 are described in the article by A. Herczog, “Microcrystalline BaTiO3, by Crystallization from Glass”, Journal of the American Ceramic Society, Vol. 47, No. 3, March 1964, pp. 107 to 115. According to the article, it is known that starting glasses can be converted into glass-ceramics by means of controlled heating, with the glass-ceramics containing not only BaTiO3 crystallites but also BaAl2Si2O8 crystallites. The crystallites have an average particle size in the range from 0.2 to 0.8 μm. The glass-ceramics have dielectric constants e′ of not more than 1200. Furthermore, glass-ceramic articles having a high dielectric constant are known from the document DE 192 80 90.
In the article “Glass ceramics containing ferroelectric phases”, Bull. Mater. Sci., Vol. 8, No. 5, December 1986, pages 557 to 565, O. Parkash, et al, describe glass-ceramics, which contain BaTiO3 crystallites and have a maximum dielectric constant at crystallite sizes in the submicron range from 0.2 to 0.8 μm.
Sintered glass-ceramics which have a high dielectric constant and comprise small, conductive grains based on BaTiO3 and/or SrTiO3 in the size range from about 0.5 μm to 10.0 μm surrounded by a thin, microcrystalline, insulating barrier layer having a thickness of from about 0.01 μm to 0.1 μm at the grain boundary are known from EP 0 378 989 A1.
Intrinsic size effects in BaTiO3 glass-ceramics are described in the article by D. McCauley et al., J. Am. Ceram. Soc., Vol. 81, No. 4, 1998, pp. 979 to 987.
Glass-ceramics based on Ba/SrTiO3 for capacitors having high energy densities are described in the article by E. P. Gorzkowski, et al, Glass-ceramics of barium strontium titanate for high energy density capacitors, J. Electroceram. 2007, Vol. 18, pp. 269 to 276.